ES2643025T3 - Process to produce a coated product - Google Patents

Description

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DESCRIPTION

Process to produce a coated product Field

The present invention relates to a process for preparing a thin, substantially uniform coating on a product, preferably a controlled release product, and more preferably a fertilizer.

Background

Fertilizers have been used for many years to supplement nutrients in culture media.

In recent years, the field of fertilizers has focused on techniques to deliver controlled amounts of plant nutrients to the soil or other culture media. The objectives of controlled fertilizer release are: 1) ensure that growing plants are not deprived of nutrients, and 2) ensure that nutrient over-supply is avoided. An over-supply of nutrients can result in toxicity to plants or lost by leaching. The controlled release of fertilizers provides an improvement in the efficiency of fertilizer use and can reduce the rate and frequency of nutrient application.

A controlled release product that has a low coating weight or a thin coating is desirable to save manufacturing costs, since less coating is required. However, to have a good slow release profile, the coating must be substantially uniform. This is difficult to achieve in a thin coating, because during conventional coating processes the coating is often damaged or its integrity is impaired.

Surprisingly it has been found that, if the coating process is separated into two stages, an application stage and a stabilization stage, in which different operating parameters (i.e. mechanical manipulation of the substrate and coated substrate) are used for each step , a controlled release product with a low coating weight and a good slow release profile can be released.

A single operating parameter between stages of application and stabilization of the latex in a fertilizer is described in US 5,089,041 and US 5,186,732, in which a single fluidized bed is used for both stages. A similar process is described in patents US 5,188,654, US 5,256,181 and US 5,435,821 for the application of polymer to a fertilizer.

In a series of Moore patents (US 4,711,659, US 4,804,403 and US 4,969,947) a polymeric topcoat is created by applying a first layer that chemically bonds to the fertilizer and a second layer that joins a fertilizer Chemically to the first layer. Although a rapid rotation drum is described in the Examples for the application stage, a change of the operating parameter for the stabilization stage is not described.

A process for coating a fertilizer with polymer is also described in US Patent 6,358,295. The turning movement described for the application stage apparently is maintained for the stabilization stage.

It has also been suggested that when a polymer coating is applied, the fertilizer particles should be kept moving at low shear and low impact, relative to each other during the coating process (i.e., soft mixing): Us 5,538 patents .531, US 5,851,261, US 5,698,002, US 6,358,296, US 6,364,925 and US 6,503,288.

Composite coatings comprising a polymer and an additive / filler have also been described in US 6,663,686, US 2004/0020254 and US 2004/0016276, but only a single parameter is described in the patent and in the publications operational

In addition to polymeric coatings, other coatings have also been used, such as a cement or cement / elastomer coating (US Patent 4,023,955); an amine or mixture of amine with a microcrystalline wax, paraffin or synthetic wax (US Patent 6,475,259); a combination of alkylamine mineral oil (US 4,150,965 and US 4,220,463); and a urea-lignosulfonate binder (US Patent 5,238,480). In these cases, different operating parameters have not been described for the stages of application and stabilization.

A nitrogen-based coating material for calcium has also been described in US Patents 5,997,601 and US 5,917,110. These patents do not describe a change in operating parameters between the stages of application and stabilization. In these patents, the problem of agglomeration of coated particles by the application of a conditioning agent is avoided.

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The patent literature also describes the coating of a sulfur fertilizer alone or in combination with a polymer or other coating material. There are problems inherent in the coating of a fertilizer with sulfur. In fertilizers coated only with sulfur, specific processing parameters should be used to avoid undesirable forms of sulfur, which crack, resulting in the loss of controlled release properties (see, for example, US 3,903,333 or US 5,405,426 ). Pretreatment of the fertilizer may be necessary to avoid these problems: US Patents 3,903,333 and US 5,653,782.

Temperature control throughout the coating process is also a key factor (US Patent 3,903,333).

The controlled release properties of sulfur-coated fertilizers can also be improved using a top layer of polymer as in the case of US Patents 5,219,465, US 5,405,426 and US

5,466,274. Wax based sealers have also been used (US patents 4,042,366, US 5,300,135, US

5,466,274, US 5,478,375 and US 5,984,994). Attempts have also been made to improve the controlled release properties of sulfur-coated fertilizers, mechanically mixing sulfur and fertilizer (US Patent 4,857,098). Polymer-sulfur-polymer coated fertilizers have also been used (US Patent 6,338,746).

EP1121975 describes a process for multilayer coating of bulk granulated material.

WO93 / 06941 describes a process for the continuous coating of fertilizer substrate particles using a plurality of fluidized beds.

US Patent 3,365,288 describes slow-acting fertilizers and their production by coating fertilizers with drying oils and then drying the coatings.

GB 2,064,995 describes a granulation method that uses a source bed. US 4,857,098 describes the production of sulfur coated urea granules.

US 5,858,094 and US 6,537,611 describe machine systems and processes for producing wear-resistant controlled release fertilizer.

US 2005/076687 discloses a method and an apparatus for coating fertilizer in granules or other form for imparting release characteristics over time and the resulting coated granule product.

Summary

In a first broad aspect of the invention, a process is provided for substantially uniformly coating a substrate, in which the coated substrate is substantially free of surface defects.

Accordingly, in a further aspect of the invention, there is provided a process for producing a coated product comprising: (a) coating a substrate with a coating material to form a coated substrate; and (b) stabilize the coated substrate to form the coated product; wherein the operative parameter of the substrate-substrate contact and of the coated substrate-coated substrate differs between stage a) and stage b), so that in stage b) the contact is minimized.

In a further aspect of the invention, the two-stage process of the invention increases productivity by optimizing the operational parameters between the application and stabilization stages.

According to an embodiment that is not part of the present invention, an apparatus is provided for producing a coated product comprising: (a) means for coating a substrate with a coating material to form a coated substrate; (b) means for stabilizing the coated substrate to form the coated product; and (c) means for providing different operating parameters for coating the substrate and stabilizing the coated substrate, whereby the means for stabilizing the coated substrate minimize contact between the coated substrate particles.

The present invention relates to a process for producing a coated product in a rotating drum comprising:

a) coating a substrate with a coating material in an application area of the rotating drum that rotates at a first circumferential speed of the drum to form a coated substrate; Y

b) stabilize the coating material on the coated substrate in a rotating drum stabilization zone that rotates at a second circumferential speed to form the coated product;

in which the first circumferential speed of the drum is maintained in the range of about 14 meters per minute to about 40 meters per minute and the second circumferential speed of the drum is maintained

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in the range of about 10% to about 80% of the first circumferential speed of the drum for a duration of between about 0.5 minutes to about 20 minutes, and in which the coating material comprises C30 + wax and a thermoset polymer formed by reaction of castor oil, or a mixture of castor oil with other polyols, and an isocyanate, or a mixture of isocyanates.

Brief description of the drawings

Figure 1 is a controlled release profile showing the effect of the drum's RPM on the release rate.

Figure 2 is a controlled release profile showing the effect of the RPM on the release rate after a simulated damage test.

Figure 3 is a controlled release profile showing the effect of the monomers ultrasonic premix.

Detailed description

The process of the invention can be applied to a variety of substrates, with fertilizer or nutrient materials from plants or other substrates related to agriculture being preferred. However, other examples of substrates include drugs, vitamins, etc. - any substrate for which a thin, substantially uniform coating (for example, controlled release) is beneficial.

If a fertilizer or nutritive material of the plant is coated, the fertilizer or nutritive material of the plant preferably comprises a water soluble compound. Preferably, the plant nutrient comprises a compound containing nitrogen, phosphorus, potassium, sulfur, micronutrients, or a mixture thereof. A preferred plant nutrient comprises urea. Other examples of useful plant nutrients are ammonium sulfate, ammonium phosphate, diamonic phosphate and mixtures thereof. Examples of useful micronutrients include copper, zinc, boron, manganese, iron and mixtures thereof. Useful plant nutritional materials are also described in US 5,538,531 and US 6,358,296. In a substrate a coating according to claim 1 is used. A thermosetting coating is used. The thermostable polymer is a polyurethane or a substituted polyurethane. As defined in claim 1, the thermosetting polymer is formed by reacting a polyol or a mixture of polyols and an isocyanate or a mixture of isocyanates. The polyol is castor oil or a mixture of castor oil with other polyols. The other polyol can be any hydroxy terminated polyol, such as a polyether, polyester, polycarbonate, polydiene, polycaprolactone, or a mixture thereof. Polyols such as hydroxy-terminated polyhydrocarbons, hydroxy-terminated polymorphs, fatty acid triglycerides, hydroxy-terminated polyesters, hydroxymethyl-terminated polyesters, hydroxymethyl-terminated perfluoromethylenes, poly (alkylene ether glycols), polyalkylene-arylene-arylene are preferred. glycols and polyalkylene ether triols. Preferred polyols include polyethylene glycols, adipic acid-ethylene glycol, poly (butylene glycol), poly (propylene glycol) and hydroxy terminated polybutadiene (see, for example, British Patent No. 1,482,213). Most preferred are polyoleters and most preferred are polyoleters having a molecular weight in the range of about 60 to about 20,000, more preferably about 60 to about 10,000 and most preferably about 60 to about 8,000.

Preferred polyols are also described in US Patent 5,538,531. In US Patent 5,538,531 polyols having from about 2 to about 6 hydroxy groups are described, and preferably have at least one C10-C22 aliphatic moiety.

The polyol can also be derived from natural sources, such as soybeans, corn, canola and the like. Polyols derived from natural sources can be used as is or can be used to derive a synthetic polyol, such as a synthetic polyol based on soybean oil, which is commercially available from Urethane Soy Systems Corp. (Princeton, Illinois) .

Another useful class of polyols are oil polyols, as described in US Patent 6,358,296.

A mixture of polyols can also be used, for example, castor oil with ethylene glycol, castor oil with polyol oil, castor oil with polyethylene glycol, castor oil with polypropylene glycol, or a mixture of polypropylene (or polyethylene) glycol of different groups terminals and molecular weights.

Any suitable isocyanate can also be used. Generally, the isocyanate compound suitable for use can be represented by the general formula:

Q (NCO) i

in which i is an integer of two or more and Q is an organic radical that has the valence of i. Q may be a substituted or unsubstituted hydrocarbon group (for example, an alkylene or arylene group). In addition, Q can be represented by the formula:

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Q1-Z-Q1

wherein Q1 is an alkylene or arylene group and Z is selected from the group comprising -O-, -OQ1-, CO-, -S-, -S-Q1- S- and SO2-. Examples of isocyanate compounds that fall within the scope of this definition include hexamethylene diisocyanate, 1,8-diisocyanate-p-naphthalene, xylyl diisocyanate, (OCNCH2CH2CH2OCH2O) 2, 1-methyl-2,4-diisocyanoccyclohexane, phenylene diisocyanates , toluylene diisocyanates, chlorophenylene diisocyanates, diphenylmethane diisocyanate, 4,4'-naphthalene diisocyanate, 1,5-triphenylmethane diisocyanate, 4,4'4'-isopropylbenzene triisocyanate and isopropylbenzene isopropylene diisocyanate.

In another embodiment, Q may also represent a polyurethane radical having a Valencia of i. In this case, Q (NCO) i is a compound that is commonly referred to in the art as a pre-polymer. Generally, a prepolymer can be prepared by reacting a stoichiometric excess of an isocyanate compound (as described above) with an active hydrogen containing compound, preferably the polyols described above. In this embodiment, the polyisocyanate, for example, can be used in proportions of about 30 percent to about 200 percent stoichiometric excess with respect to the hydroxyl ratio in the polyol.

In another embodiment, the isocyanate compound suitable for use in the process of the present invention can be selected from dimers and numbers of isocyanates and diisocyanates and from polymeric diisocyanates having the general formula:

[Q "(NCO) i] j

in which both i and j are whole numbers that have a value of 2 or more, and Q "is a polyfunctional organic radical. Such isocyanates can be used together with compounds having the general formula:

L (NCO) i

in which i is an integer that has a value of 1 or more and L is a monofunctional or polyfunctional atom or radical. Examples of isocyanate compounds that fall within the scope of this definition include ethyl phosphonic diisocyanate, phenylphosphonic diisocyanate, compounds containing a group = Si-NCO, sulfonamide-derived isocyanate compounds (QSO2NCO), cyanic acid and thiocyanic acid.

See also, for example, British Patent No. 1,453,258 for other examples of useful isocyanate compounds.

Non-limiting examples of suitable isocyanates include: 1,6-hexamethylene diisocyanate, 1,4-butylene diisocyanate, furfurylidene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4'-diisocyanate of diphenylmethane, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenylpropane diisocyanate, 4,4'-diphenyl-3,3'-dimethylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1-methyl-2 , 4-diisocyanate-5-chlorobenzene, 2,4-diisocyanate-s-triazine, 1- methyl-2,4-diisocyanate-cyclohexane, p-phenylenediisocyanate, m-phenylenedisocyanate, 1,4-naphthalene diisocyanate, dianisidine diisocyanate , bitoluene diisocyanate, 1,4-xylylene diisocyanate, 1,3-xylylene diisocyanate, bis- (4- isocyanophenyl) methane, bis- (3-methyl-4-isocyanophenyl) methane, polymethylene polyphenyl polyisocyanates and mixtures thereof.

Particularly preferred isocyanates are those described in US 5,538,531 and US 6,358,296.

For some coatings an isocyanate mixture may be preferred.

Preferably, the polyol and isocyanate are used in amounts such that the ratio of NCO groups in the isocyanate to hydroxy groups in the polyol is in the range of about 0.5 to about 3.0, more preferably about 0.8 to about 2.0 and most preferably from about 0.9 to about 1.1. A C30 + wax is included in the coating as an additive. Other additives may be included in the coating materials. For example, if the coating materials are hydrophilic, then they will be compatible with hydrophilic substrate surfaces and will be easy to spread on the surface. However, if the coating materials are hydrophobic, there will be difficulty in spreading the coating materials on the surface of the substrate. In these circumstances, additives such as wetting agents, flow agents, leveling agents and coupling agents can be used to improve the spreading ability. If the viscosity of the coating is high, an additive can also be used to improve the spreading capacity.

Another function of the additives is to increase the hydrophobicity of the coating. Hydrophobic additives reduce the release rate of the coated substrate.

Preferred additives are organic additives, such as petroleum products, carbon products, natural products and synthetic products. Lubricants derived from these can also be used. Exemplary organic additives include commercially available coating additives and paint additives (such as

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wetting agents, flow agents, leveling agents and coupling agents), wax, paraffin oil, bitumen, asphalt, carbon-derived oil, canola oil, soybean oil, coconut oil, flaxseed oil, tung oil, Vegetable wax, animal fat, animal wax, and forest products such as resin oil, modified resin oil, taloil pitch and tar. Mixtures of these materials can also be used. Particularly preferred organic additives are hydrophobic materials. The wax is a C30 + wax, such as those available in the Chevron Phillips Chemical Company market.

The amount of organic additive may vary, depending on its end in the mixture. For example, for some commercially available additives, an amount as low as 0.001% by weight of the coating composition can be used.

Preferred organic additives and their amounts are those that improve the release profile and mechanical manipulation of the polymer coated substrate.

The process of the invention comprises a first application stage in which a coating is uniformly applied to a substrate, followed by a second stabilization stage in which contact between the coated particles or their relative movement is minimized. In each of these stages, the operating parameters are different, preferably substantially different.

The application stage followed by the stabilization stage can be repeated as many times as necessary or as desired to form multiple layers of coating on the substrate.

It is worth noting that the substrate does not have to be spherical and non-spherical substrates do not have to be removed before coating. The present process can be used to coat a whole stream of substrate as it is produced in a granulator or the like.

The application stage is performed in a rotating drum. According to an embodiment that is not part of the present invention, the application step can be carried out in a mixer (such as a screw mixer or a ribbon mixer) or in a fluidized bed. In the application stage, vigorous agitation is desirable. The intensity of the turning, mixing or rotation of the substrate can be controlled by the speed of rotation of the drum (for example, RPM), by increasing or decreasing the diameter of the drum, by mechanical means, such as by adding a rotary mixer, baffles or plows, or combinations thereof. These and other methods for controlling the speed of rotation of a substrate in a rotating drum are known to one skilled in the art. Intense or rapid flipping, mixing or rotation of the particles is desirable; as achieved by a fast drum speed. A preferred drum speed is greater than about 15 rpm, preferably, between about 15 and about 40 rpm, more preferably between about 20 and about 30 rpm, and even more preferably about 24 rpm, for a drum having a diameter of about 1 foot (30.5 cm).

The movement of particles inside the drum can be described by the average linear velocity.

The average linear velocity (Vave) of a particle moving in the circumferential of a rotating drum can be expressed by the following formula (I):

Vave = 27T (r / t) (I)

where r is the radius of the drum and t is the time for a rotation of the drum.

Thus, by increasing the radius of the drum, the average linear velocity of the particles can be increased.

The average linear speed can also be increased by increasing the drum RPM.

In the application stage, a high linear velocity is desirable. The drum speed in terms of circumferential is greater than about 14 mpm (meters per minute), between about 14 and about 40 mpm, more preferably between about 20 and about 30 mpm and even more preferably about 24 mpm.

However, the above formula (I) for the Vave and the preferred drum speeds indicated above are only valid when the inner surface of the drum is smooth. When the drum includes baffles, the movement of the particle is influenced by the baffle structure. The preferred drum speeds mentioned above will therefore vary with structural changes in the drum in order to obtain optimum mixing results and spreading results of the coating materials on the substrate granules.

Particle movement within the drum can also be described by the drum's RPM / CRPM ratio (critical RPM). The critical RPM are the RPM in which a single particle remains stationary on the edge of the drum due to the centrifugal forces.

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The CRPM (Nc) are given by the following formula (II):

Nc = V (g / 27t2D) (II)

in which D is the diameter of the drum and g is the gravitational acceleration.

Therefore, by increasing the diameter of the drum, the CRPM can be reduced.

In the application stage, a desirable RPM / CRPM ratio is in the range of approximately 1360%.

In a preferred embodiment, the RPM / CRPM ratio is 15-50%, more preferably between about 17 and about 45%, more preferably still between about 20 and about 40% and even more preferably about 25- 35%

The previous interval for the RPM / CRPM ratio, however, is only valid when the inner surface of the drum is smooth. When the drum includes baffles, the movement of the particle is influenced by the baffle structure. The preferred ratios mentioned above will therefore vary with structural changes in the drum in order to achieve optimal mixing results and spreading results of the coating materials on the substrate granules.

The duration of the application stage will depend on a number of factors, including the rate of change in the viscosity of the coating material. During the polymerization process for a thermoset polymer, the viscosity of the coating material will increase with the degree of polymerization, which is related to time. When the viscosity reaches a certain value, the application stage must cease and the stabilization stage must begin. If the viscosity of the coating raw materials is low and the viscosity increase is slow over time, then a longer application stage and less vigorous agitation can be applied than when the viscosity of the coating raw materials is high. and the increase in viscosity is rapid over time.

Temperature also plays an important role in the change in the viscosity of the coating materials. The higher the temperature, the faster the increase in viscosity will be and, therefore, a shorter coating time and more vigorous agitation will be required to achieve a uniformly coated substrate substantially free of surface defects.

In any case, when agitation or mixing is potent, the application stage will be of a shorter duration.

If strong agitation is provided, a higher coating temperature can be used and the time for the application stage decreases. A shorter coating time will increase productivity.

In order to achieve a uniform coating, substantially free of surface defects, (1) the duration of the application stage, (2) the viscosity of the coating material, (3) the degree of agitation or mixing and (4) the Application stage temperature is optimized according to the above considerations.

The optimal combination of these parameters depends largely on the nature of the coating materials and the equipment used for the coating process. The optimal combination of these parameters can be determined by routine experimentation.

When a polyol and an isocyanate are used for a coating, the application stage will generally require approximately 2 minutes in a rotating drum that has a diameter of approximately 1 foot (30.5 cm), rotating at approximately 24 rpm and that is maintained at a temperature of approximately 75 ° C. The coating components in the form, for example, of polymer melts, or reactive components or solutions or mixtures thereof, can be contacted sequentially or simultaneously with the surface of the substrate. If the coating components are brought into contact with the substrate surface simultaneously, a polymer premix is usually used (in which the components are reacted or partially mixed before application) or a prepolymer is used as described above If other additives are used, such as organic additives, these can be premixed with one or more of the components or the prepolymer or premix or they can be applied sequentially to the surface of the substrate in any order with the components, the prepolymer or the premix . The coating components can be introduced into the drum by any means, such as by spraying or dripping onto the surface of the particles or into the substrate bed. In addition, some of the coating components may be added to the substrate before the substrate is added to the coating apparatus.

Once the coating has been applied and a uniform coating has been achieved, the stabilization step is carried out. For the stabilization stage, contact between the coated particles is minimized. A medium

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To minimize contact is to minimize sudden agitation of the coated particles. The contact between the coated particles is minimized to minimize damage to the coating, such as the coating that is torn from the coated substrate and / or caves or depressions formed on the coating. Damage to the coating may result in an irregular coating thickness. The stabilization stage is the polymer curing stage for thermostable polymers. During the curing stage for thermostable polymers, the viscosity of the polymer increases significantly, and the polymer becomes thick. When the viscosity reaches a certain value, the coating materials will become adherent. The period of time measured from the beginning of the polymerization reaction to this "adherent" stage is called "gelation time".

Using traditional coating processes, during curing, especially during the gelation time, the coated fertilizer granules come into contact giving rise to lumps that clump together and defects (such as irregular coating thickness, craters, tears, holes, etc.) that are formed on the coating surface. To avoid or reduce the number of defects, the contact between the coated particles should be minimized during the stabilization stage.

Again, a means to minimize contact is to minimize sudden agitation of the coated particles.

The stabilization step can be performed on any device that achieves the result of minimizing contact between coated particles. According to the present invention a rotating drum is used. According to an embodiment that is not part of the present invention, a screw mixer, a tape mixer or a fluidized bed can be used for the stabilization step. If a rotating drum is used, without baffles, etc., the drum speed should be slow, preferably from about 10% to about 80% of the application stage, more preferably from about 20% to about 80% , even more preferably from about 30% to about 80%, and even more preferably about 40% to about 80%. If a drum having a diameter of about 1 foot (30.5 cm) is used, preferably, the drum speed is less than about 15 rpm, more preferably between about 1 and about 15 rpm, more preferably still between about 2 and about 12 rpm, and even more preferably still between about 3 and about 12 rpm. By decreasing the size of the drum (for example, from about 10% to about 80% of the size of the drum at the application stage), the average linear velocity of the particles and the RPM / CRPM ratio will also decrease, minimizing contact between coated particles and sudden agitation of the particles. The flipping, mixing or rotation of the particles can also be controlled by mechanical means, such as the deflector structure.

The duration of the stabilization stage depends on the coating and the selected temperature. Generally, for polymer coatings, the stabilization will last between about 0.5 and about 20 minutes, preferably between about 1 and about 10 minutes, more preferably between about 2 and about 8 minutes, and more preferably still, between about 2 and about 5 minutes

Other processing parameters, such as post-stabilization temperatures and cooling times, will depend on the nature of the substrate to be coated and the nature of the polymer used as the coating.

The process of the invention can be carried out discontinuously or continuously. The apparatus of the invention can be a one-piece device or a two-piece or more piece of equipment. Different combinations of equipment can be used for the apparatus, such as a first rotating drum in sequence with a second rotating drum, rotating at different speeds, with different diameters, etc .; an individual rotating drum that changes its mixing power in the middle of the operation; an individual rotating drum having two regions of different diameters; etc.

A preferred apparatus is an individual drum, which changes its mixing power in the middle of the operation by adjusting the drum structure, such as, the deflector structure and the deflector angles, using additional mechanical devices (such as a rotating mixer in the bed of substrate, a comb-shaped device submerged in the bed of substrate or mixing bars), modifying the diameters, and / or modifying the speed (for example, a drum equipped with a speed variator).

Devices that improve the mixing power at the application stage include stirrers, combs or mixing bars, or baffles. If an individual drum with an application and stabilization zone is used, different deflector structures can be included in each zone. If different deflector structures are used in each zone, a higher deflector may be used in the application zone than in the stabilization zone, or deflectors having a different angle along the axial length of the drum may be used in the areas of application and stabilization. If deflectors having different angles along the axial length are used in the application and stabilization zones, then the angle must be selected in the application zone that helps to mix the substrate and / or move the substrate backwards to Increase mixing power and relative mixing time. You can also use baffles in the application area that have a comb or wave structure that improves the mix. You can also select devices for the application area for

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minimize coating damage. The stabilization zone may have baffles along the axial length of the drum that help minimize the disturbance of the coating on the substrate to reduce damage to the coating. The baffles in the stabilization zone can be selected so that the angle and / or shape contribute to minimizing the damage to the coating. If more than one piece of equipment is used for the application and stabilization stages, stirrers, combs or mixing bars or baffles can be selected according to the above principles for each of the application and stabilization stages.

The following examples are offered by way of illustration and not by way of limitation.

Example 1

A sample of 1 kg of urea was loaded into a 12-inch (30.5 cm) diameter drum and heated while rotating at 75 ° C with an electric thermal gun. A mixture of 18% by weight of C30 + wax in castor oil was heated to 115 ° C in an electric oven. A volume of this mixture equivalent to 6.7 grams and an isocyanate volume equivalent to 2.3 grams were applied simultaneously to the urea at 75 ° C. After 6 minutes of rotation a second identical layer was applied. A 3rd layer was applied after an additional 6 minutes. 6 minutes after the 3rd layer was applied, the heat source was removed and the sample was cooled with compressed air. After 12 minutes, the sample had cooled below 30 ° C, drum rotation was stopped and the sample was removed. The product coating weight is 2.7%, based on the weight of the substrate. The results are shown in Figure 1.

In Figure 1, the rpm of the drum was adjusted for the different tests by modifying the motor speed, with the revolutions divided, the speed of the drum (motor) was reduced 2 minutes after applying the coating reagents.

As can be seen from the results of Figure 1, a rapid stirring coating stage followed by a slow stirring stabilization stage greatly improves the controlled release profile of the fertilizer product produced compared to those produced using a single operating parameter.

The water release profile for the controlled release fertilizer material was determined according to the following process.

Water release profile test

An analysis of the water release rate profile was performed using a Technicon AutoAnalyzer ™, calibrated and used in accordance with the teachings of Automated Determination of Urea and Ammoniacal Nitrogen (University of Missouri, 1980). The following procedure was used:

1. Weigh accurately 15 grams (± 0.1 mg) of the sample on a weighing plate. Record the weight of the sample. Transfer the sample to a 125 ml Erlenmeyer flask.

2. Add 75 ml of demineralized water and cover the flask.

3. Gently shake the sample and water until all the particles are submerged.

4. Let the sample stand for a specified time at a constant temperature (usually at room temperature).

5. Gently shake the flask to mix the solution and decant only the solution to a 100 ml volumetric flask.

6. Rinse the sample with demineralized water by adding it to the volumetric flask.

7. Empty volumetric flask volume and mix well.

8. If the essay must be repeated for another period of time, repeat starting from stage 2.

9. Once the Technicon AutoAnalyzer II is in line, transfer part of this solution (or make the required dilutions if necessary) to the Technicon sample cups for analysis.

10. Record the results in parts per million N-NH3 (read directly in a Shimadzu Integrator).

The water release profile of controlled release products produced in accordance with the process of the invention is improved with respect to those produced using conventional processes.

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Example 2

The samples produced in Example 1 (Figure 1) were subjected to simulated handling damage in the paint stirrer test. After the simulated damage test, the samples were analyzed again for water release. The effects of different RPM are evident after the simulated damage test. The results are shown in Figure 2.

Paint shaker simulation test

The "paint stirrer simulation" test used to simulate the damage to the controlled release coating is carried out in a paint stirrer machine. The first 200 grams of the controlled release fertilizer is placed in a metal can 6 "in diameter by 5.5" deep with a lid. Next, 8 machine screws (1/4 inch by A inch) with slotted heads and 8 square head nuts (1/4 inch) are added to the can. The can with controlled release fertilizer, nuts and bolts is then placed safely in a paint conditioner / stirrer (Red Devil, model% H.P.). The test sample is vigorously conditioned in the paint stirrer at a frequency of 730 cycles per minute for 6 minutes. The operating time is controlled with an electronic timer (Gralab model 451) that automatically stops the paint stirrer at the preset time. After completing the cycle in the paint stirrer, the can is removed and the nuts and bolts are removed by passing the contents through a 3A mesh sieve. The controlled release fertilizer is collected in a saucepan and returned to its sample bag for the analysis of the release rate.

As can be seen from the results in Figure 2, even after the simulated damage test, the controlled release profile of the controlled release products produced by the present invention is improved with respect to those produced when a single operating parameter is used.

Example 3

In this Example, the effect of ultrasonically premixing the monomers is considered. A sample of 1 kg of urea was loaded into a 12-inch (30.5 cm) diameter drum that rotated at 24 rpm and was heated while rotating at 75 ° C with an electric thermal gun. A mixture of 18% by weight of C30 + wax in castor oil was heated to 115 ° C in an electric oven. A volume of this mixture equivalent to 12.8 grams and an isocyanate volume equivalent to 5.2 grams were mixed by ultrasound for 30 seconds before 9 grams of the mixture was applied to the urea lamination bed at 75 ° C. After 6 minutes of rotation, a second identical layer was prepared and applied. After an additional 6 minutes a 3rd layer was applied. 6 minutes after the 3rd layer was applied, the heat source was removed and the sample was cooled with compressed air. After 12 minutes, the sample had cooled below 30 ° C, drum rotation was stopped and the sample was removed. Next, the water release rate profile for the controlled release fertilizer material was determined.

The release profile of the ultrasonically mixed reagents is compared with that of a similar sample that was produced with the same reactants applied simultaneously to the rolling bed. The results are shown in Figure 3.

As can be seen from the results of Figure 3, by premixing the monomers, an improved controlled release profile is achieved. This indicates that the ultrasonic mixing improves the uniformity of the coating; for example, the ratio of castor oil to isocyanate. A better blend not only improves the uniformity of the thickness of the coating on different substrate granules, but also improves the uniformity of the chemical composition of the coating in an individual granule. The ultrasonic mixture is an extreme mixture. With the ultrasonic mixing, the viscosity of the coating materials will increase significantly. Therefore, although it can improve the uniformity of the chemical composition, the ultrasonic mixing also increases the difficulty of achieving a uniform coating thickness, because the viscosity of the coating materials increases. Thus, if premixed or prepolymer coating materials are used in the process of the present invention, there is an optimal combination between viscosity and mixing capacity at the application stage.

It should be noted that, as used in the specification and in the appended claims, the singular forms of "a" and "the" include the plural reference unless the context clearly indicates otherwise.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as those skilled in the art to which this invention pertains are understood in a conventional manner.

Claims (20)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1. A process for producing a coated product in a rotating drum comprising: a) coating a substrate with a coating material in an application area of the rotating drum that rotates at a first circumferential speed of the drum to form a coated substrate; Y b) stabilize the coating material on the coated substrate in a rotating drum stabilization zone that rotates at a second circumferential speed to form the coated product; characterized in that the first circumferential speed of the drum is maintained in the range of about l4 meters per minute at about 40 meters per minute and the second circumferential speed of the drum is maintained in the range of about 10% to about 80% of the first circumferential speed of the drum with a duration of between about 0.5 minutes and about 20 minutes, and because the coating material comprises a C30 + wax and a thermosetting polymer formed by reaction of castor oil, or a mixture of castor oil with other polyols, and an isocyanate, or a mixture of isocyanates. 2. The process of claim 1, wherein the substrate is a plant nutrient, a drug or a vitamin. 3. The process of claim 1, wherein the substrate is urea. 4. The process of claim 1, wherein the castor oil, or a mixture of castor oil with other polyols, and isocyanate, or a mixture of isocyanates, is applied sequentially or simultaneously. 5. The process of claim 1, wherein the castor oil, or a mixture of castor oil with other polyols, and isocyanate, or a mixture of isocyanates, is applied simultaneously and ultrasonically premixed. 6. The process of any one of claims 1 to 5, wherein stage a) and stage b) are carried out on different rotating drums. 7. The process of any one of claims 1 to 5, wherein stage a) and stage b) are carried out on different rotating drums having different diameters, characterized in that the drum diameter for stage b ) is lower than for stage a). 8. The process of claim 7, wherein the drum diameter for stage b) is about 10 to about 80% lower than for stage a). 9. The process of any one of claims 1 to 5, wherein stage a) and stage b) are carried out in a rotating individual drum, which has a first zone and a second zone characterized in that the first zone has a diameter greater than the second zone. 10. The process of claim 9, wherein the diameter of the drum in the first zone is about 10% to about 80% higher than in the second zone. 11. The process of any one of claims 1 to 5, wherein stage a) and stage b) are carried out in a rotating individual drum that changes its mixing power between stage a) and stage b ) reducing its speed and adjusting the drum structure. 12. The process of any one of claims 1 to 11, wherein the second circumferential speed of the drum is in the range of about 20% to about 80% of the first circumferential speed of the drum. 13. The process of any one of claims 1 to 11, wherein the second circumferential speed of the drum is in the range of about 30% to about 80% of the first circumferential speed of the drum. 14. The process of any one of claims 1 to 11, wherein the second circumferential speed of the drum is in the range of about 40% to about 80% of the first circumferential speed of the drum. 15. The process of any one of claims 1 to 14, wherein the second circumferential speed of the drum is maintained at approximately 12 meters per minute. 16. The process of any one of claims 1 to 14, wherein the first circumferential speed of the drum is in the range of about 20 to about 30 meters per minute, such as about 24 meters per minute. 17. The process of any one of claims 1 to 16, wherein step b) is carried out over a period of between about 1 and about 10 minutes, such as between about 2 and about 8 minutes, for example, between about 2 and about 5 minutes The process of any one of claims 1 to 16, wherein step b) is carried out during a period of approximately 4 minutes. 19. The process of any one of claims 1 to 16, wherein step a) is carried out for a period of approximately 2 minutes. 10 20. The process of any one of claims 1 to 19, wherein step a) is carried out at a temperature of about 75 degrees Celsius. 21. The process of any one of claims 1 to 19, wherein step b) is carried out at a temperature of about 75 degrees Celsius.